Lots of hyperbole and down right misinformation has been spouted about from both sides of the Civil War proponents. Slavery was most certainly a part of the secession as was taxation and states rights issues. As for the assertion that secession is Constitutionally granted? I do not believe that is clearly stated. The Preamble does give us the impression that the founders believed that when a government no longer represents the populace that they are free to leave...just as we did the English Monarchy. It is though pretty clear that Lincoln was indeed prepared to give the South concessions to keep the Union intact even though he eventually came to believe(and rightly so) that Slavery was an abomination. The issue was an evolving conflict with Lincoln. He came to the conclusion after years of personal debate. It was not his early view. In fact...He was very far from an abolitionist in his early years.